diff --git a/lib/bcoin/coin.js b/lib/bcoin/coin.js
index 063586ec..420a4c59 100644
--- a/lib/bcoin/coin.js
+++ b/lib/bcoin/coin.js
@@ -83,8 +83,10 @@ utils.inherits(Coin, bcoin.output);
  */
 
 Coin.prototype.getConfirmations = function getConfirmations(height) {
-  if (height == null)
-    height = network.height;
+  assert(typeof height === 'number');
+
+  if (height === -1)
+    return 0;
 
   if (this.height === -1)
     return 0;
@@ -131,7 +133,7 @@ Coin.prototype.inspect = function inspect() {
     coinbase: this.coinbase,
     hash: this.hash ? utils.revHex(this.hash) : null,
     index: this.index,
-    age: this.getAge(),
+    age: this.getAge(network.height),
     address: this.getAddress()
   };
 };
diff --git a/lib/bcoin/mtx.js b/lib/bcoin/mtx.js
index 0d1d4d65..a61f113e 100644
--- a/lib/bcoin/mtx.js
+++ b/lib/bcoin/mtx.js
@@ -1297,8 +1297,7 @@ MTX.prototype.sortMembers = function sortMembers() {
  */
 
 MTX.prototype.avoidFeeSniping = function avoidFeeSniping(height) {
-  if (height == null)
-    height = network.height;
+  assert(typeof height === 'number');
 
   if (height === -1)
     height = 0;
diff --git a/lib/bcoin/tx.js b/lib/bcoin/tx.js
index c8ae440d..fe25f84f 100644
--- a/lib/bcoin/tx.js
+++ b/lib/bcoin/tx.js
@@ -1362,11 +1362,10 @@ TX.prototype.getPriority = function getPriority(height, size) {
   if (this.isCoinbase())
     return new bn(0);
 
-  if (height == null) {
-    height = this.height;
-    if (height === -1)
-      height = network.height + 1;
-  }
+  assert(typeof height === 'number');
+
+  if (height === -1)
+    height = 0;
 
   if (size == null)
     size = this.maxSize();
@@ -1411,11 +1410,7 @@ TX.prototype.getPriority = function getPriority(height, size) {
 TX.prototype.isFree = function isFree(height, size) {
   var priority;
 
-  if (height == null) {
-    height = this.height;
-    if (height === -1)
-      height = network.height + 1;
-  }
+  assert(typeof height === 'number');
 
   priority = this.getPriority(height, size).priority;
 
@@ -1483,8 +1478,10 @@ TX.prototype.getMaxFee = function getMaxFee(size, rate) {
  */
 
 TX.prototype.getConfirmations = function getConfirmations(height) {
-  if (height == null)
-    height = network.height;
+  assert(typeof height === 'number');
+
+  if (height === -1)
+    return 0;
 
   if (this.height === -1)
     return 0;
@@ -1635,8 +1632,8 @@ TX.prototype.inspect = function inspect() {
     value: utils.btc(this.getOutputValue()),
     fee: utils.btc(this.getFee()),
     minFee: utils.btc(this.getMinFee()),
-    confirmations: this.getConfirmations(),
-    priority: this.getPriority().priority.toString(10),
+    confirmations: this.getConfirmations(network.height),
+    priority: this.getPriority(network.height).priority.toString(10),
     date: utils.date(this.ts || this.ps),
     block: this.block ? utils.revHex(this.block) : null,
     ts: this.ts,
diff --git a/lib/bcoin/wallet.js b/lib/bcoin/wallet.js
index 2b0d2cdf..4f10df3c 100644
--- a/lib/bcoin/wallet.js
+++ b/lib/bcoin/wallet.js
@@ -815,7 +815,7 @@ Wallet.prototype.createTX = function createTX(options, outputs, callback) {
     // if (options.locktime != null)
     //   tx.setLocktime(options.locktime);
     // else
-    //   tx.avoidFeeSniping();
+    //   tx.avoidFeeSniping(network.height);
 
     // Sign the transaction
     if (!self.sign(tx))